The simplest way to understand the tectonic forces reshaping the media landscape, and social media in particular, is to talk to teenagers. “I use Snapchat to talk to my friends one-on-one, but Instagram is where everyone in my life is,” one told me, offering a concise summation of the new-media hierarchy. She hasn’t deleted Facebook, she said, but she doesn’t really use it. “I don’t even have the app on my phone,” she added. Retail clients, of course, will pay gobs of money for insights such as these, and not without good reason. The children are our future, but nowhere more so than on Madison Avenue and in Silicon Valley, where aging Boomers have made it their life’s mission to deconstruct and monetize successive generations of aspiring consumers. Among the big-name players in the retail-consulting space is the asset-management firm Piper Jaffray, whose semi-annual survey of teens has become a bona fide Rosetta Stone for financial analysts seeking to understand Generation Z.

The latest edition of Taking Stock with Teens confirms much of what we already know: teenagers are rapidly turning away from cable television, if they even know what that is, in favor of mobile-video platforms such as YouTube and streaming services such as Netflix. (In a somewhat more surprising development, Tommy Hilfiger and Crocs appear to be making a comeback.) But the survey also serves as a barometer for who’s up and who’s down in the equally cutthroat battle for social-media supremacy. According to Piper Jaffray, Instagram and Snapchat have been neck and neck in popularity for some time: in spring 2018, 83 percent of teens told the firm they used Snapchat at least once a month, while 82 percent said the same of Instagram. But in the firm’s most recent survey, Instagram is gaining ground: 84 percent of teens say they use Snapchat at least once a month, while 85 percent say the same of Instagram. Snapchat still reigns in one area: 46 percent of teens surveyed say Snapchat is their favorite social network. Despite its apparent omnipresence, only 32 percent say the same about Instagram.

Snapchat may still be a crucial communication tool for Gen Z, but Piper Jaffray’s findings reflect the company’s recent struggles. The app has been slowly waning in popularity among all age groups, particularly after a redesign that most teens despised, and that even Evan Spiegel has seemingly come to regret—“We slowed down our product and eroded our core product value,” he lamented in a memo to employees. Snap’s stock price recently tumbled to just above $7, and one analyst predicted that Spiegel will have to beg for cash next year. “While it is obvious that Snap wasn’t prepared for life as a public company, it now has a more pressing problem. It is quickly running out of money,” Michael Nathanson of MoffettNathanson wrote.

When it comes to Facebook, the picture is even bleaker. In the short term, Facebook remains a massive force; it has a $441 billion market cap, commands about 20 percent of the digital-advertising market, and generated nearly $16 billion in net income last year from the estimated 2.5 billion people who use at least one of its apps. But declining use among teens suggests the new-user pipeline may be drying up. Only 36 percent of teens say they use Facebook once a month, and just 5 percent call it their favorite social platform. “Current 15-year-olds are using F.B. at an ~28 percent rate, if engagement does not improve over cohort life, suggests declines in young user penetration for core Facebook, incrementally increasing the importance of the I.G. and WhatsApp platforms for overall F.B.,” Piper Jaffray’s senior analysts concluded. Much of the burden for growth, in other words, will fall to Facebook’s more popular acquisitions. But in recent months, the founders of Instagram and WhatsApp have left their respective companies, leaving Mark Zuckerberg (an elder millennial, himself) to re-assert control. Already, he’s introduced features that tie Instagram more tightly to Facebook, including prompts to connect to Facebook or open the Facebook app in the Settings and Notifications section. So far, it’s unclear how Instagram’s users will respond to the changes. But at least one has met with disapproval. “I’ve only ever tapped into the IGTV icon by accident,” one teen told me, “because it’s right next to D.M.s.”